1. Field of the Invention
The present invention relates to an electronic blood pressure monitor that electronically measures blood pressures and to a method of managing measurement data; In particular, the invention relates to an electronic blood pressure monitor that stores in a memory measurement data taken over a long period of time and to a method of managing the measurement data.
2. Description of the Background Art
With the widespread use of home electronic blood pressure monitors, electronic blood pressure monitors are used for various purposes. This trend is created by the increase of the number of persons who are now in good health and regularly measure the blood pressure at home for the purpose of preventing lifestyle-related diseases, except for those who have conditions diagnosed as hypertension and undergo medical treatment at hospitals. Such a practice would be highly preferable particularly in the current environment of the aging society and tight budgets for social insurance.
There are various blood pressure variation patterns. For example, the blood pressure varies at relatively short intervals in synchronization with breathing, varies depending on physical and mental activities, shows circadian variation (variation in a day), weekly variation (variation in a week), seasonal variation, and variation with age. The circadian variation is generally well-known and given relatively great attention for measurement of the blood pressure. In other words, it has been recommended to measure the blood pressure at the same time every day to obtain necessary information regarding blood-pressure variation and thereby exclude any unnecessary information about the blood-pressure variation. Other types of variations of the blood pressure, however, have been given little attention and consequently an erroneous diagnosis could be made based on a single measurement reflecting these types of variations. For example, the blood pressure varies in a week (weekly variation). In general, the blood pressure of many people is high on weekdays and decreases on weekends. If this weekly variation is ignored and the blood pressure is measured on any weekday of a week and then measured on Saturday or Sunday of another week to compare these measurements of the blood pressure with each other, the comparison could erroneously be made due to overlapping of the weekly variation and the actual variation of the blood pressure. In case of conventional blood pressure monitors, user merely write and keep on a recording sheet measurement values taken each time the blood pressure is measured, and even those monitors having a memory basically show a list of measurement values over a few months at most. Therefore, it is a disadvantage of the conventional blood pressure monitors that observation of the blood pressure in consideration of the above-described blood-pressure variations is difficult.
Moreover, if the blood pressure is monitored for the purpose of preventing lifestyle-related diseases of those who are now in good health as mentioned above, the monitoring period would be a long period of years. Although the issue of how frequently the blood pressure is measured should be considered, a greater memory capacity is necessary for storing measurement values of the blood pressure measured over such a long period of time, resulting in an increase in cost. Technical approaches for solving this problem have been proposed by the applicant of the present application. According to the proposed approaches a device is used that has the function of storing a representative value of measurement data obtained by measuring (detecting) such information about a living body as blood pressure (Japanese Patent Laying-Open No. 2000-41953) and a device is used that displays time-series data of averages of measurement data (Japanese Patent Laying-Open No. 11-239566).
The device of Japanese Patent Laying-Open No. 2000-41953 has a reduced memory capacity achieved by determining a representative value of detected information at predetermined intervals to store the representative value while detecting information about a living body. However, measurement data taken in a predetermined period of time immediately preceding the present time cannot be checked since the data has already been converted into representative data.
The device of Japanese Patent Laying-Open No. 11-239566 merely displays averages for example of blood-pressure values taken in a predetermined period of time on monthly basis for example. Therefore, this device cannot provide finer data about the variation like variation in a week or circadian variation. Under the circumstances, there have been demands for improvements in display manner of measurement data.